Head suspensions for disk storage devices typically include a load beam, a flexure, and a base plate. The load beam typically includes a mounting region at a proximal end of the load beam for mounting the head suspension to an actuator of a disk drive, a rigid region at a distal end of the load beam, and a spring region between the mounting region and the rigid region. The base plate is mounted to the mounting region of the load beam to facilitate the attachment of the head suspension to the actuator. The flexure is positioned at the distal end of the load beam, and typically includes a gimbal region having a slider mounting surface to which a slider having a magnetic read/write head is mounted. The head slider is thereby supported in read/write orientation with respect to a rotating disk. The gimbal region is resiliently moveable with respect to the remainder of the flexure in response to aerodynamic forces acting on the head slider in the presence of an air bearing generated by the rotating disk. The spring force provided by the spring region counteracts the aerodynamic lift force generated by the head slider in the presence of the air bearing and causes the head slider to “fly” over the surface of the disk at a pre-determined height known as the fly height.
In one type of head suspension, the flexure is formed as a separate component and includes a mounting region that is rigidly mounted at the distal end of the load beam using conventional approaches, such as spot welds. In such a flexure, the gimbal region is located distally from the load beam mounting region of the flexure and generally includes a cantilever beam having the slider mounting surface to which the head slider is mounted. A dimple or other load point extends between the load beam and the slider mounting surface of the flexure and is formed in either the load beam or the slider mounting surface of the flexure. The dimple transfers the spring force generated by the spring region of the load beam to the flexure and the head slider to counteract the aerodynamic force generated by the air bearing between the head slider and the rotating disk. In this manner, the dimple acts as a “load point” between the flexure/head slider and the load beam. The dimple also provides clearance between the cantilever beam of the flexure and the load beam, and serves as a point about which the head slider can gimbal in pitch and roll directions in response to fluctuations in the aerodynamic forces generated by the air bearing.
As the number and density of magnetic domains on the rotating disk increase, it becomes increasingly important that the head slider be precisely aligned over the disk to ensure the proper writing and reading of data to and from the magnetic domains. The angular position of the head suspension and the head slider, also known as the static attitude, is calibrated so that when the disk drive is in operation the head slider assumes an optimal orientation at the fly height. It is therefore important that the static attitude of the head suspension and head slider be properly established. Toward this end, the head slider must be properly positioned on the flexure with respect to the dimple. Misalignments between the dimple and the head slider may cause a torque to be exerted on the head slider, and thus affect the fly height of the head slider and the orientation of the head slider at the fly height. Moreover, improper fly height and angular positioning of the head slider over the disk could result in the head slider “crashing” into the disk surface as the head slider gimbals due to the close proximity of the head slider to the rotating disk at the fly height.
Electrical interconnection between the read/write heads on the head slider and circuitry in the disk storage device is provided along the length of the head suspension. Conventionally, one or more conductive copper traces are bonded to the stainless steel load beam with a dielectric adhesive or are otherwise formed on the load beam, to provide electrical interconnection. Such an integrated lead or wireless head suspension may include one or more bond pads at the distal end of the traces to which terminals on the head slider are electrically connected. Misalignment between the head slider (and therefore the terminals on the head slider) and the bond pads of the traces may compromise the integrity of the electrical interconnection between the head slider and the electrical circuitry in the disk storage device. Therefore, in addition to being properly positioned on the flexure to promote desirable properties such as fly height and static attitudes, the head slider must also be aligned on the flexure relative to the bond pads to ensure a high quality interconnection between the bond pads and the terminals of the head slider.
The traces and bond pads may also be configured to provide desired mechanical connection and support to the gimbal region of the load beam. In one approach, described in U.S. Pat. No. 5,491,597 (Bennin, et al.) the traces include one or more symmetrical torsional arms extending from the load beam. Adjacent arms are shaped as back to back “P”s, with a semicircular indentation approximately at the middle of each back. The indentation defines a round clearance hole that fits around and receives the gimbal pivot (e.g., dimple). This allows the head assembly to swivel on the gimbal pivot.
To assist in the alignment of the head suspension components and in the formation of head suspension features, the head suspension typically includes reference apertures or tooling holes that are engaged by an alignment tool. The apertures are typically longitudinally spaced apart and are formed in the rigid region of the load beam. In head suspensions that include a separate flexure mounted to the load beam, the flexure can include corresponding apertures formed in the load beam mounting region of the flexure. The reference apertures in the load beam and the flexure are typically circular, and are sized and positioned so as to be substantially concentric when the flexure is mounted to the load beam.
Rigid cylindrical pins on an alignment tool are typically used to align the individual head suspension components. The rigid pins are spaced apart an amount equal to the longitudinal spacing between the reference apertures in the components. The pins are inserted into and engage the apertures in the load beam and flexure, and in this manner concentrically align the apertures, and thus the load beam and the flexure, to one another. A similar method may be used to install the head slider to the slider mounting surface of the gimbal region of the flexure.
According to one approach described in U.S. Pat. No. 6,657,821 (Jenneke), a reference aperture is provided with a compliant feature configured to receive a tapered cylindrical pin for precisely locating a head suspension component relative to a desired reference. A spring beam tab of the compliant feature is engaged by the tapered pin to reliably locate the pin within the reference aperture. In an approach illustrated in U.S. Pat. No. 5,570,249 (Aoyagi et al.), rather than being circular, a distal aperture in the load beam is elongated and generally elliptical. The aperture includes a “v” shaped portion at one end. According to another approach described in U.S. Pat. No. 6,625,870 (Heeren et al.), an elongated alignment aperture is formed in a rigid region of a load beam, and a proximal alignment aperture and a distal alignment aperture are formed in the flexure. The elongated aperture overlaps at least a portion of the proximal and distal alignment apertures. Once aligned, the components can then be fastened together, as by welding or other known processes.
FIG. 1 is an illustration of a portion of a prior art head suspension assembly 10. Head suspension 10 was used to support and properly orient a head slider over a rotating disk (not shown) in a magnetic disk storage device. Head suspension 10 was comprised of a load beam 12 coupled at a proximal end to an actuator arm (not shown). A stainless steel flexure 14 was mounted to a distal end of the load beam 12. The flexure 14 was attached to a carrier portion or strip 16 detachable from the remainder of the flexure 14 at line 18. Flexure 14 was formed with a gimbal region 20 having a slider mounting surface 22 for receiving a head slider 24 (shown partially cut away) having electrical terminals 26. Integrated leads 28 were formed on flexure 14 to provide electrical interconnection between the electrical terminals 26 of the head slider 24 and circuitry in the magnetic disk storage device to which the head suspension 10 was mounted. Integrated leads 28 included one or more conductive traces 30 that provided such electrical interconnection. The traces 30 terminated in a plurality of bond pads 32 on the slider mounting surface 22 at the gimbal region 20 of the flexure 14. The bond pads 32 were formed in a layer of copper separated from the stainless steel of the flexure 14 by a layer of dielectric material interposed therebetween.
The head suspension 10 included a circular aperture 34 extending through the flexure 14 at the carrier strip 16. The aperture 34 was formed in a copper layer. That is, the aperture 34 included an opening in the stainless steel of the flexure 14 and an opening in a copper region formed on the stainless steel. The opening through the stainless steel was larger than the opening in the copper so that the edges of the aperture 34 were defined by copper. The aperture 34 was engageable by a tooling pin as described previously for assisting alignment of the bond pads 32 of the traces 30 to the load beam 12 and dimple 183, thus assisting in the accuracy of the placement of the slider 24 in subsequent procedures.
There are various deficiencies and shortcomings associated with prior art head suspensions and tooling. Conventional reference apertures such as those described above include manufacturing tolerances that affect the interface between the alignment tool and the head suspension component. The pins on the alignment tools also include manufacturing and positioning tolerances. These tolerances are cumulative so as to affect the alignment of individual head suspension components, and affect the forming of head suspension features, such as the load point dimple, and mounting of the head slider to the flexure. In addition, when aligning individual head suspension components, the manufacturing tolerances in the apertures of the load beam and the flexure are “stacked” together because the head suspension components are engaged by common alignment pins, thus creating additional alignment problems.
A drawback to these prior art approaches is that the tooling pin is typically aligned to a reference feature (i.e. the reference or alignment aperture) formed in a stainless steel region of the load beam or flexure. When aligning a component such as the head slider to the bond pads, one must assume that the registration of the stainless steel layer of the reference aperture is perfect with respect to the copper layer of the bond pads. However, perfect alignment between the stainless steel layer and the copper layer is not typical.
The traces and bond pads are often formed on the load beam through etching (subtractive) or deposition (additive) processes. Conventional etching processes make use of a laminate including a dielectric layer between stainless steel and copper layers. Using known photolithography and etching processes, regions of the copper layer are subjected to etching or corrosive chemicals, which etch or remove the copper to form specific features, for example, traces and bond pads. The mass of these formed copper components is inversely related to the length of time the copper is subjected to etching chemicals. Thus, as the copper components are subject to the etching process, areas of copper mass become smaller and openings or apertures in areas of copper become larger. Small variations in processing, including etching time, can sometimes lead to variations in the size and location of the copper components, including the traces and bond pads. Such variations can result in misalignment of the electrical terminals of the head slider to the bond pads.
For example, it is possible for the head slider to be positioned on the flexure so as to promote certain properties, such as fly height and static attitude, yet be mis-aligned relative to the bond pads due to bond pad positional variation so as to form none or a low quality electrical interconnection. Conversely, the terminals of the head slider may be adequately aligned to the bond pads to form a high quality interconnection, yet because of positional variation of the bond pads, the position of the head slider on the flexure adversely effects such characteristics as fly height of the head slider and static attitude of the head suspension assembly.
There is, therefore, a continuing need for an improved method and structure for aligning individual head suspension components, for aligning the head slider to the bond pads on the flexure and for establishing the proper static attitude of the head suspension assembly.